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Evaluation of Options for Reducing Irish Diesel Particulate Emissions - Utilising Measurement and Modelling Methods

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Complete with results
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STRIA Roadmaps
Transport mode
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Transport policies
Environmental/Emissions aspects
Transport sectors
Passenger transport,
Freight transport


Background & Policy context

Exhaust emissions from newly manufactured vehicles and diesel engines are heavily regulated by EU Directives (due to their adverse health effects) but very little data is currently available from any source which quantifies actual on-road diesel particulate emissions. This is especially the case for older, poorly maintained diesel vehicles.

Data collected from the 'Snap Acceleration' test currently used by the Department of the Environment and Local Government for annual testing of commercial diesel vehicles (as part of the National Car Test) cannot easily be correlated with real life PM (particulate matter) emissions.

The data that is available for Irish cities does not distinguish between particulate matter resulting from diesel engines and that from other sources (e.g. other forms of combustion, building work, naturally occurring particles). The fraction of particulates being emitted by diesel vehicles is therefore not known, nor is the percentage of it that is attributed to older, less well maintained vehicles.

In a 1993 report, the UK based Quality of Urban Air Review Group found that road vehicles account for 94% of black smoke emissions in London and it can be assumed that the figure for Dublin would be similar. Air quality monitoring stations in Dublin report that at city centre locations, such as College Green, PM10 (particulate matter with a mean diameter of less than 10 microns) level exceed the EU limit of 50 µg/m3 for approximately one out of every three days (EPA Air Quality Monitoring Annual Report 1999). EU council directive 1999/30/EC of April 1999 directs member countries to take action to prevent the concentrations of PM10 in the ambient air from exceeding this limit. Thus the need exists to examine the effect of different policies designed to reduce the total amount of PM being produced in Ireland in order that the optimum strategy is implemented to meet the required European standards.

Whist current legislation sets standards for air quality and for emissions from new vehicles, emissions from older, high polluting vehicles are not seriously monitored or controlled. The current government vehicle emissions test procedures are not at all rigorous in respect of diesel particulates. In order to come up with effective policies for Ireland regarding particulate emissions it is necessary to first determine accurately the amount of particulates being emitted from on-road vehicles. It is hoped that this project will help in attaining this resu


EU council directive 1999/30/EC directs member countries to take action to prevent the concentrations of PM10 in the ambient air from exceeding specified limits. The EPA Air Quality Monitoring Annual Report 1999 identifies problem areas in Dublin city centre which appear to be strongly linked with high traffic impacts.


The aim of this project is to identify the most cost effective strategy for reducing the amounts of harmful particulates emitted from diesel-engine vehicles in the Irish context. In order to do this, it is first necessary to determine more precisely than the current amount of PM being emitted, and to be able to find out which vehicles are the biggest polluters. The collating of such data is one of the main aims of this project. Using this data, dispersion models can be employed to examine the effects of different policies (such as the overhauling of older vehicles engines, the limiting of the number of older vehicles, the limitation on time that older vehicles are allowed in to the city etc.). Recent work by A.W. Reynolds & B.M. Broderick at Trinity College Dublin (published in Transportation Research Part D 5 (2000) 77-101) identified specific weaknesses in the quality of Emissions Factors available and this project aims to address these. Having examined the net effects of different policies using environmental economics analysis tools, the final aim of this project is to determine with some confidence which policy would be the most appropriate for Ireland to significantly reduce the amount of PM produced by diesel vehicles.


The proposed project can be split into three separate phases:

  • Phase 1: The refinement and use of a new diesel particulate measurement system to enable gathering of PM emissions data in real-life situations.
  • Phase 2: The use of computer models to examine the localised effects of PM pollution
  • Phase 3: The use of the tools of environmental economics and policy to assess the effects of different PM abatement strategies.

The aims and objectives of each of these stages are as follows:

Phase 1 Objectives:
- Design and commissioning of a novel PM measurement system
- Design and coding of a data acquisition program for engine testing
- Conduction of a comprehensive series of emission tests to evaluate the new measurement system
- Establishment of correlations between this and other established PM measurement techniques


The first phase of this project will involve the use of a new measurement system for diesel particulates, developed at the Department of Mechanical Engineering, UCD. Using a ceramic diesel particulate filter and a gravimetric approach the total amount of particulates emitted from a vehicle over a journey can be accurately determined.

Correlations between results from this method with those from more established PM measurement techniques will be established, utilising the diesel engine test facilities of the Department of Mechanical Engineering, UCD. An emissions test facility will be designed and constructed such that tests can be conducted on a Ford 2.5 litre high speed, direct injection turbocharged diesel engine. Exhaust gas analysis equipment as well as measurement equipment already designed and built within UCD will be incorporated into this facility. This equipment includes Bosch Smoke Test Equipment, Gas Analysis Equipment (for carbon dioxide, carbon monoxide, oxygen, hydrocarbons, oxides of nitrogen), Smoke Opacity Meter and a mini dilution tunnel (used to mimic the dilution effect of the atmosphere on tailpipe emissions). Temperature, pressure, torque, speed, fuel flow, turbocharger and air intake measurement equipment will also included in the test facility. A removable insert will added to the rig piping in order to determine the amount of particulates deposited on the walls of the exhaust piping. Data acquisition equipment will be automated and controlled from a computer located in the engine control room, adjacent to UCD's diesel engine test cell. This test facility will be used to run a series of comprehensive emissions tests. Factors affecting the condensing of hydrocarbons, the ignition temperature of particulate matter and the amount of deposits on the pipes need to be investigated.

The relationship between particulate matter and NOX will also be addressed. Issues relating to the differences between emissions testing on an engine test bed and that from an on-road vehicle will also be examined. Correlations between the different measurement techniques incorporated into the test equipment will also be established so that measurements taken with one method can be converted into the units of another. Once the advantages and limitations of the new measurement methodology have been established in a laboratory situation, vehicle trails will be conducted. One of the aims of these trials is to examine the differences between re


Parent Programmes
Institution Type
Public institution
Institution Name
Department of the Environment, Heritage and Local Government/administered by the Environmental Protection Agency (EPA)
Type of funding
Public (national/regional/local)


This research project set out to answer the following three questions that were formulated after a comprehensive and wide ranging examination of the literature concerning diesel particulate matter (DPM):

  1. How much DPM is actually emitted by vehicles as they are driven about on Irish roads, under real-world driving conditions?
  2. What are the burdens imposed on a roadside pedestrian when a diesel vehicle passes by? What is the concentration, and composition, of DPM pollution that s/he will experience?
  3. What are the best DPM reduction strategies for Ireland?

It was initially hoped to integrate all three phases of this research in a robust manner, whereby the data on-road emissions data collected during the first phase could be used in the other two phases. Resource limitations prevented the collection of large quantities of data and thus the second and third phases of the research relied on European emission estimates and not on measured on-road data obtained from real world driving under Irish conditions, as was envisaged.

A combination of experimental work, computer modelling and data collection and analysis was used in an attempt to answer the three research questions above. The wide scope of this project resulted in the development of a deep understanding by the author of a wide range of topics, but none of the answers resulting from this work were straightforward.

On-road Measurement of Diesel Particulate Matter:

  • Diesel particulate matter is one of the most difficult pollutants to understand, research and quantify. It is defined by a complicated and time consuming, laboratory-based measurement system that cannot easily be applied in on-road measurement. Estimates of DPM emissions are obtained from laboratory-based testing and not from diesel vehicles as they are driven in the real world, with normal loads and subject to realistic traffic conditions. A simple, straight-forward and easy to apply on-road DPM measurement system would generate useful emissions data that does not exist at present, and would enable more precise identification of poorly maintained, high-polluting diesel vehicles.
  • No commercial on-road measurement system currently exists that can quantify real-world DPM emissions, but a prototype of such a system was developed in the course of this project. The numerous difficulties associated with developing a portable DPM measurement system for in-vehicle use were detailed and discussed. The unsuitability of legislative test m

    Policy implications

    During the course of this project much of the available literature regarding diesel particulate matter was examined. Despite being researched intensively for the last number of decades, gaps in the knowledge and understanding of DPM remain. This project has taken important first steps in deepening the scientific knowledge regarding DPM, especially regarding the fate of this pollutant once it has exited the tailpipe.

    The following are some of the topics that should be addressed in the future in order to fully comprehend diesel particulate matter:

    • Despite considerable resource limitations, a prototype diesel particulate and sampling measurement system was developed during the course of this project, and has the potential to provide useful on-road emissions data. A chemical speciation of the collected diesel particulate matter and comparison to the legislative test method are required for further refinements to be made. While this research has been an important pilot project additional resources are required to reveal the full potential of the new measurement system.
    • The lack of an on-road DPM measurement system, and the data it could provide, was apparent in all the research areas addressed by this project. Accurate models and emissions inventories require real world emissions data, while the benefits of inspection and maintenance programs would be improved if a quick and precise DPM measurement system were available. 
    • The dispersion modelling approach followed in this research should be further refined. Validation of the dispersion model and inclusion of wind effects could be investigated. A more advanced model that takes the CFD calculated dispersion concentrations values and used them to calculate the amount of adsorption, nucleation and particle coagulation that occurs in a dispersion plume would prove invaluable in deepening our understanding of DPM. The adsorption model should be updated to include multi-component evaporation and condensing.
    • The adverse health effects of DPM are well documented but the actual biological mechanism by which it causes harm is not yet fully understood. The complicated physical and chemical nature of DPM, together with the significant number of confounders present in any epidemiological study, undermines attempts to determine the relevant causal health effects mechanism with any degree of certainty. Research must continue to determine the toxicological relevant parameter of DPM, particularly in circumstances where the solid frac


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